Quantum cryptography uses quantum mechanical effects to perform cryptographic tasks transmitting secure communications over networks. For example, using quantum key distribution (QKD), a secure communication may be transmitted between two parties (usually referred to as Alice and Bob) using a predefined and shared key such that a third party (usually referred to as Eve) is unable to identify the key.
There are generally two ways secure communications are currently transmitted using optical signals, through free space optics (FSO) or over a fiber optic network. Using polarization coding in FSO, a photon may be transmitted between two parties, with the photon at a specific state of polarization. Generally, if the parties know the state of polarization, the secure communication may be decoded.
In fiber optic networks, however, the state of polarization of a photon over an optical fiber may change during its passage through the fiber. In theory, optical fibers should preserve a state of polarization. In practice, however, a wave entering an optical fiber having a definite state of polarization may come out on the other end with a different random state of polarization due to micro-disturbances in the optical fiber. This means that a linearly polarized incident optical signal may become elliptically polarized when it exits the fiber. As such, the current art seeks to find alternative means to transmit secure communications without relying on the state of polarization across a fiber optic network.
Currently within the art, researchers are seeking to increase the transmission speed of the secure communication between the two parties using quantum cryptography to increase speed of communications. Additionally, researchers are looking for cryptography protocols that may be communicated over large distance, use fewer resources, but still have enhanced security for transmission between the parties without interference from an outside party due to man-in-the-middle attacks, photon siphoning attacks, plaintext-cipher text attacks, and the like.